Idler device for magnetic recording/reproducing apparatus

ABSTRACT

An idler device of the magnetic recording/reproducing apparatus is disclosed having the construction that an idler arm is inserted to the side of a clutch shaft which is installed at a lower surface of a main chassis. Without an extra construction for the assembly, a snap engagement is possibly made, so that a workability of an assembly working is improved and the number of parts can be reduced, and thus, a production cost can be reduced. In addition, the assembly of an idler gear is completed as a plate spring is fixed to an idler shaft in a state that the idler gear is inserted in the idler shaft of an idler arm. Thus, the assembly working is relatively facilitated, and a production cost can be reduced with the simple construction. Moreover, since the plate spring is installed in a state of being fixed at the protrusion bar by the stopper, the relative position of the plate spring is precisely set with respect to the neighboring parts, so that an operation reliability can be remarkably improved.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a magnetic recording/reproducingapparatus, and more particularly, to an idler device of a magneticrecording/reproducing apparatus in which an idler gear is selectivelyrotated to be in contact with a supply reel according to a rotationaldirection of an idler gear.

[0003] 2. Description of the Background Art

[0004]FIG. 1 illustrates a tape travelling structure of a generalmagnetic recording/reproducing apparatus.

[0005] As shown in FIG. 1, a supply reel driving body 1 and a windingreel driving body 21 are installed to drive a supply reel (not shown)and a winding reel (not shown) of a tape cassette (not shown) at oneside of a main chassis.

[0006] A plurality of posts and guide rollers are installed on the mainchassis (C) to guide travelling of a tape (T) released from a tapecassette.

[0007] A tension post 3 for controlling a tensile force of a travellingtape (T) is installed at a tension arm 4.

[0008] The tension arm 4 is rotated at a predetermined angle accordingto the tension of the tape (T) on the main chassis (C) centering arounda shaft pin 2, for which the tension arm 4 is elastically supported by aspring 5.

[0009] The tape (T) having passed the tension post 3 is guided by aguide post 6 and transmitted to a full width erasing head 7.

[0010] The full width erasing head 7 removes in advance a signal whichhas been recorded on the tape in a recording mode.

[0011] An inertia roller is installed at a position past the full widtherasing head 7 to guide the travelling of the tape (T).

[0012] Next, the tape (T) is guided by guide posts 10 and 11 of thesupplying and winding side which are moved along loading paths formed atboth sides of a rotational head drum 9.

[0013] The guide posts 10 and 11 draws the tape (T) from the inside ofthe tape cassette, the position indicated in a dotted line as shown inFIG. 1, so as to be wound and traveled.

[0014] A supply slant post 12 and a winding slant post 13 are providednext to the guide posts 10 and 11 toward the rotational head drum 9, soas to guide the traveling of the tape (T).

[0015] The guide posts 10 and 11 and the slant posts 12 and 13 areinstalled on a supply and winding slant bases 14 and 15 and moved alongthe loading path.

[0016] As shown in FIG. 1, the rotational head drum 9, on which the tape(T) is wound and traveled, is provided with a rotational head (notshown) for reading a signal recorded on the tape (T) or recording asignal.

[0017] The tape (T) passes the rotational head drum 9 and the slant post13 and the guide post 11 of the winding side and then passes the audiocontrol head 16. The audio control head 16 performs deleting, recordingand reproducing of an audio signal, and recording and reproducing acontrol signal.

[0018] A guide post 17 is provided on the main chassis (C) at anadjacent location of the audio control head 16 to control the travelingheight of the tape (T).

[0019] A capstan shaft 18 for providing a traveling force to the tape(T) is installed at a position passing the guide post 17. The capstanshaft 18 is an output shaft of a capstan motor (not shown) installed atthe opposite face of the main chassis (C), and a traveling direction ofthe tape (T) is determined depending on the rotational direction of thecapstan motor.

[0020] A pinch roller 19 is installed selectively tightly-attached tothe capstan shaft 18 to provide a force for pulling the tape (T).

[0021] A winding post 20 is provided at an adjacent location of thepinch roller 19 and the capstan shaft 18. A winding arm (not shown) isinstalled and moved at the winding post 20.

[0022] Between the supply reel driving body 1 and the winding reeldriving body 21, a clutch assembly 22 is installed to drive the supplyreel or the winding reel at a certain torque regardless of the amount ofthe tape (T) wound on the supply reel or the winding reel upon receiptof a driving force from the capstan motor.

[0023] An idler gear 24 is installed at a front end of an idler arm 25which is coaxially installed with the clutch assembly 22. The idler gear24 is selectively connected to either the supply reel driving body 1 orthe winding reel driving body 21 for transferring a driving forcethereto upon receipt of a driving force from the clutch assembly 22.

[0024] A tension brake 27 is installed wound on the supply reel drivingbody 1 with its both ends fixed at the tension arm 4. The tension brake27 controls the rotational speed of the supply reel driving body 1according to the operation of the tension arm 4, thereby controlling atension of the tape (T).

[0025] The construction of the idler unit including the idler arm 25 andthe idler gear 24 will now be described with reference to FIG. 2.

[0026] First, the idler arm 25 is installed centering around the clutchshaft 22′ installed penetrating the main chassis (C) The idler arm 25 ispositioned at an upper surface of the main chassis (C) and the clutchassembly 22 is installed at the lower surface of the main chassis (C).The clutch shaft 22′, the center of the rotation of the clutch assembly22, is installed penetrating from the lower surface to the upper surfaceof the main chassis (C) and fixed as a washer 25 w is inserted at theend portion of the clutch shaft 22′.

[0027] The idler gear 24 is installed at the front end portion of theidler arm 25, so as to be rotatable centering around an idler shaft 24p.

[0028] An idler spring 25 s is installed between the idler arm 25 andthe idler gear 24. The idler spring 24 s supported by the idler gear 24is mounted on a friction member 24 f installed at the idler gear 24.

[0029] The idler spring 24 s is operated so that the idler arm 25 can berotated centering around the clutch shaft 22′ according to therotational direction of the idler gear 24.

[0030] That is, according to the rotational direction of the idler gear24, the idler gear 24 is selectively engaged with the supply reeldriving body 1 or the winding reel driving body 21 to transfer thedriving force of the capstan motor.

[0031] Reference numerals 24 g denotes a large gear and 24 g′ denotes asmall gear.

[0032] However, the idler unit of the conventional art has manyproblems.

[0033] That is, first, in installing the idler arm 25 at the uppersurface of the main chassis (C), it is to be assembled together with theclutch assembly 22.

[0034] Namely, in a state that the clutch assembly 22 is positioned atthe lower surface of the main chassis (C) and the idler arm 25 ispositioned at the upper surface of the main chassis (C), the washer 25 wis to be engaged at the end portion of the clutch shaft 22′. Thus, theassembly working is relatively complicated.

[0035] Secondly, for the installation of the idler arm 25, the washer 25w is necessarily used, creating a problem that the parts for theassembly are relatively increased in number, which results in that aproduction cost is accordingly increased and the number of assemblyworking is relatively increased.

[0036] Thirdly, in stalling the idler gear 24 at the idler arm 25, theidler shaft 24 p is to be installed after positioning the idler spring24 s in a state of a provisional assembly between the idler arm 25 andthe idler gear 24. Thus, the assembly operation is relativelycomplicated.

[0037] Fourthly, in the assembly process, if the idler spring 24 sallowing an elastic force for the idler gear 24 which is rotated betweenthe friction member 24 f and the idler arm 25 is not installed at theright position, the idler gear 24 is not properly operated.

[0038] Lastly, since the number of parts for operation of the idler gear24 is relatively many, its production cost is increased and the processnumber of the assembly working is relatively increased.

SUMMARY OF THE INVENTION

[0039] Therefore, an object of the present invention is to provide anidler device for a magnetic recording/reproducing apparatus that iscapable of minimizing the number of parts and facilitating an assemblyworking.

[0040] Another object of the present invention is to provide an idlerdevice for a magnetic recording/reproducing apparatus that is capable ofheightening a reliability in an idle operation.

[0041] To achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly describedherein, there is provided an idler device for a magneticrecording/reproducing apparatus including a clutch shaft verticallycoupled to a main chassis; an idler arm installed rotatable centeringaround the clutch shaft by having an mounting portion elasticallyengaged to the clutch shaft in a snap method in the direction of theside of the clutch shaft at one portion; an idler shaft provided at theother portion of the idler arm; an idler gear rotatably installed at theidler arm centering around the idler shaft, for selectively transmittinga driving force according to a rotational direction; and a pressingelastic member supported by an end portion of the idler shaft, forelastically pressing the idler gear in the direction of the idler arm.

[0042] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the clutch shaft is provided with asupporting portion at its side and the mounting portion of the idler armis supported by being coupled between the main chassis and thesupporting portion of the clutch shaft.

[0043] In the idler device for a magnetic recording/reproducingapparatus of the present invention, a protrusion bar is formed at theend portion of the idler shaft to support the pressing elastic member,and the pressing elastic member is supported by the protrusion bar andmade of a disk-shaped plate spring providing an elastic force to theidler gear.

[0044] To achieve the above objects, there is also provided an idlerdevice for a magnetic recording/reproducing apparatus including: arotational central shaft vertically coupled to a main chassis; and anidler arm having an mounting portion elastically engaged to therotational central shaft in a snap method at the side of the rotationalcentral shaft and an idler gear installed at the opposite of themounting portion, for selectively transmitting a driving force accordingto a rotational direction.

[0045] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the rotational central shaft is aclutch shaft and press-fit to a fixing hole of the main chassis andfixed in a riveting method.

[0046] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the rotational central shaftincludes a supporting portion formed at its circumferential surface, andthe mounting portion of the idler arm is supported by being coupledbetween the main chassis and the supporting portion of the rotationalcentral shaft.

[0047] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the supporting portion of therotational central shaft is annularly protruded from the circumferenceof the rotational central shaft.

[0048] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the mounting portion of the idlerarm includes a shaft insertion portion with one side opened so that therotational central shaft can be inserted thereinto and a separationpreventing unit formed at the opening portion of the shaft insertionportion, for not allowing separation from the rotational central shaft.

[0049] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the separation preventing unit iselastic legs elastically protruded in the direction of the shaftinsertion portion from the opened portion of the mounting portion.

[0050] In the idler device for a magnetic recording/reproducingapparatus of the present invention, a front end portion the elastic legscontacts the circumferential face of the rotational central shaft andthe space between each elastic leg is smaller than the diameter of therotational central shaft.

[0051] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the shaft insertion portion isprovided with a semicircular hitching portion closely attached to therotational central shaft at the portion facing the elastic leg.

[0052] To achieve the above objects, there is also provided an idlerdevice of a magnetic recording/reproducing apparatus including: an idlerarm installed rotatable centering around a rotational shaft of which oneside is fixed at a main chassis; an idler shaft provided at the otherside of the idler arm; an idler gear rotatably installed at the idlerarm centering around the idler shaft, for selectively transferring adriving force in the rotational direction; and a pressing elastic membersupported by the end portion of the idler shaft and elastically pressingthe idler gear in the direction of the idler arm.

[0053] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the idler arm and the idler shaftare integrally formed.

[0054] In the idler device for a magnetic recording/reproducingapparatus of the present invention, a protrusion bar is formed at theend portion of the idler shaft, at which the pressing elastic member isinstalled and supported.

[0055] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the pressing elastic member isformed as a disk type plate spring.

[0056] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the pressing elastic member includesa central plate inserted into and supported by the idler shaft, apressing ring closely attached to the idler gear, and elastic legsconnecting the central plate and the pressing ring and having an elasticforce.

[0057] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the central plate has stoppersprotruded so as for the central plate to be coupled and supported at theboth sides of the idler shaft.

[0058] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the elastic legs are extended tohave a scroll structure at the circumference of the central plate.

[0059] In the idler device for a magnetic recording/reproducingapparatus of the present invention, the elastic legs are slantinglyconnected so as for the central plate and the pressing ring to have apredetermined height difference.

[0060] With the idler device for a magnetic recording/reproducingapparatus of the present invention, since the idler arm can besnap-engaged to the clutch shaft and the plate spring is fixed to theidler shaft in a state that the idler gear is inserted into the idlershaft of the idler arm, a workability of the assembly working can beimproved and the parts can be simplified in number. Thus, a productionunit cost can be reduced.

[0061] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and together with the description serve to explain theprinciples of the invention.

[0063] In the drawings:

[0064]FIG. 1 is a plan view showing a tape traveling structure of ageneral magnetic recording/reproducing apparatus;

[0065]FIG. 2 is a sectional view taken along line ‘A-A’ of FIG. 1showing an idler device of a magnetic recording/reproducing apparatus inaccordance with a conventional art;

[0066]FIG. 3 is a sectional view showing the construction of an idlerdevice of a magnetic recording/reproducing apparatus in accordance witha preferred embodiment of the present invention;

[0067]FIG. 4 is a plan view of the idler device in accordance with thepreferred embodiment of the present invention;

[0068]FIG. 5 is a plan view showing the construction of a plate springin accordance with the preferred embodiment of the present invention;and

[0069]FIG. 6 is a side view showing the construction of the plate springin accordance with the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0070] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings.

[0071] There may be a plurality of embodiments of an idler device of amagnetic recording/reproducing apparatus in accordance with the presentinvention, of which a preferred embodiment will now be described.

[0072]FIG. 3 is a sectional view showing the construction of an idlerdevice of a magnetic recording/reproducing apparatus in accordance witha preferred embodiment of the present invention.

[0073] As shown in FIG. 3, a clutch shaft 42 of a clutch assembly isinstalled downwardly extended at a lower surface of a main chassis 40.

[0074] A supporting portion 44 is formed at the lower end of the clutchshaft 42, that is, at a position adjacent to the lower surface of themain chassis 40.

[0075] The supporting portion 44 is formed to be annularly protrudedhaving a diameter larger than that of other portions of the clutch shaft42, so as to support an idler arm 50.

[0076] A journal portion 45 is formed at an upper portion of the supportportion 44 of the clutch shaft 42, to which the idler arm 50 is closelyattached.

[0077] A fixed portion 45 is formed at an upper portion of the journalportion 45, press-fit to a fixing hole 41 of the main chassis 40.

[0078] The upper portion 46 a of the fixed portion 45 is press-fit tothe fixing hole 41 of the main chassis 40 and fixed to the main chassis40 in a riveting method.

[0079] The idler arm 50 is integrally formed with the idler shaft 52,and an idler gear 60 is installed at the idler shaft 52. The front endof the idler gear is rotated at a certain angle centering around theclutch shaft 42 in the rotational direction of the idler gear, so thatthe idler gear 60 can selectively transfer a driving force to the supplyreel or the driving reel.

[0080] In order to install the idler arm 50 to the clutch shaft 52, withreference to FIG. 4, a mounting portion 54 is formed at one side of theidler arm 50.

[0081] A shaft insertion portion 55 is formed at the center of themounting portion, into which the clutch shaft 42 is inserted.

[0082] A hitching portion 57 is formed at a rear portion of the shaftinsertion portion 55 and hitched by the supporting portion 44. Thehitching portion 57 has a semicircular structure as shown in FIG. 4 andan extended portion 57 a is formed at the lower side thereof, where thesupport portion of the clutch shaft 42 is positioned.

[0083] A front side of the shaft inserting portion 55 is opened where anopening portion 56 is formed allowing an insertion in the side directionof the clutch shaft 42.

[0084] Elastic legs 58 and 58′, a separation preventing unit, are formedlong extended toward the center of the shaft inserting portion 55 fromthe both ends of the opening portion 56.

[0085] The space between the front ends of the elastic legs 58 and 58′is formed to be smaller than the diameter of the clutch shaft 42. Theelastic legs 58 and 58′ support the outer surface of the journal portion45 of the clutch shaft 42 so that the clutch shaft 42 may not bearbitrarily released from the shaft inserting portion 55.

[0086] An idler shaft 52 is formed integrally connected through themounting portion 54 and the connecting portion 53 at the other end ofthe idler arm 50. The connecting portion 53 has a double-bent slantportion 53 a.

[0087] In the preferred embodiment, the idler shaft 52 is integrallyformed with the idler arm 50, but not necessarily limited thereto solong as it is fixed to the idler arm 50.

[0088] A protrusion bar 52 a is formed at a front end of the idler shaft52, having a relatively smaller diameter in the axial direction.

[0089] The idler gear 60 is installed rotatable centering around theidler shaft 52 of the idler arm 50.

[0090] The idler gear 60 renders the idler arm 50 to be rotatedcentering around the clutch shaft 42 according to its rotationaldirection.

[0091] At the idler gear 50, a pressed face 62 is formed in a ring shapeat a lower surface (in view of the drawing), in which the pressing ring76 of the plate spring 70 (to be described) is mounted.

[0092] The idler arm 50 includes a large gear 64 and a small gear 66 fortransferring a driving force.

[0093] The plate spring 70, the pressing elastic member, is used so thatthe idler gear can be elastically pressed by the idler arm 50 and thusthe idler arm 50 can be rotated in the rotational direction of the idlergear 60.

[0094] As shown in FIGS. 5 and 6, the plate spring 70 includes adisk-type central plate 72 at the center thereof.

[0095] The central plate 72 is for a connection with the protrusion bar52 a and includes stoppers 73 at the inner side. The stoppers 73, whichis slantingly bent by cutting the central plate 72 so as to face eachother, is installed at the side of the protrusion bar 52 a. Theprotrusion bar 52 a may have a groove 52 b for inserting the stopper 73.

[0096] At the circumference of the central plate 72, a plurality ofelastic legs 75 are formed in a scroll structure. The elastic leg 75 hasan elastic force in view of its material and shape characteristics, andthe pressing ring 76 is connected to its front end portion.

[0097] The pressing ring 76 is annularly formed and mounted in thepressed face 62 of the idler gear 60. Since the elastic legs 75 areslantingly formed, the pressing ring 76 has a certain height differencewith the central plate 72.

[0098] The operation of the idler device for a magneticrecording/reproducing apparatus constructed as described above will nowbe explained.

[0099] First, the idler arm 50 is fixed at the clutch shaft 42. That is,the clutch shaft 42 of the clutch assembly is installed protruded at thelower surface of the main chassis 40.

[0100] At this time, the fixed portion 46 of the clutch shaft 42 ispress-fit to the fixing hole 41 of the main chassis 40 and then theupper portion is pressed in a rivet method, so that the clutch shaft 42is firmly fixed at the main chassis 40.

[0101] Next, the idler arm 50 is inserted at the lower end of the clutchshaft which is installed at the lower face of the main chassis 40. ATthis time, the idler arm 50 is inserted into the clutch shaft 42 fromthe side of the clutch shaft 42 in the direction of the arrow ‘A’ ofFIG. 3.

[0102] That is, the idler arm 50 is positioned at the lower surface ofthe main chassis 40, and the opening portion 56 of the mounting portion54 is inserted between the support portion 44 of the lower end of theclutch shaft 42 and the main chassis 40. Then, the clutch shaft 42 isinserted into the shaft inserting portion 55 through the opening portion56.

[0103] At this time, the front ends of the elastic legs 58 and 58′ areelastically transformed in the direction of being opened to each otherby the clutch shaft 42.

[0104] When the clutch shaft 42 is completely inserted into the shaftinserting portion 55, the elastic legs 58 and 58′ are restored, so thatthe elastic legs 58 and 58′ and the hitching portion 57 support theouter surface of the clutch shaft 42.

[0105] The hitching portion 57 a of the idler arm 50 is hitched by thesupport portion 44, so that the idler arm 50 does not move along theclutch shaft 42.

[0106] Installation of the idler gear 60 at the idler arm 50 will now bedescribed.

[0107] First, the idler gear 60 is inserted into the idler shaft 52. Thecentral plate 72 of the plate spring 70 is pressed down at theprotrusion bar 52 a of the idler shaft 52, so that the stopper 73 can beinserted at the both sides of the outer circumference (or the groove) ofthe protrusion bar 52 a.

[0108] Then, the pressing ring 76 is mounted in the pressed face 62 ofthe idler gear 60, so that the idler gear 60 can be pressed to the idlerarm 50 with an elastic force. At this time, the elastic force isprovided by the elastic leg 74 of the plate spring 70.

[0109] The idler gear 60 installed in this manner is rotated uponreceiving the driving force provided from the capstan motor. At thistime, the idler arm 50 is rotated according to the rotational directionof the idler gear 60. This rotation is made because the idler gear 60 ispressed to the idler arm 50 by the elastic force of the plate spring 70.

[0110] As so far described, the idler device of the magneticrecording/reproducing apparatus of the present invention, with theconstruction that the idler arm is inserted to the side of the clutchshaft which is installed at the lower surface of the main chassis, hasmany advantages.

[0111] That is, for example, first, without an extra construction forassembly, a snap engagement is possibly made, so that a workability ofthe assembly working is improved and the number of parts can be reduced,and thus, a production cost can be reduced.

[0112] Secondly, the assembly of the idler gear is completed as theplate spring is fixed to the idler shaft in a state that the idler gearis inserted in the idler shaft of the idler arm. Thus, the assemblyworking is relatively facilitated, and a production cost can be reducedwith the simple construction.

[0113] Lastly, since the plate spring is installed in a state of beingfixed at the protrusion bar by the stopper, the relative position of theplate spring is precisely set with respect to the neighboring parts, sothat an operation reliability can be remarkably improved.

[0114] As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the meets and bounds of theclaims, or equivalence of such meets and bounds are therefore intendedto be embraced by the appended claims.

What is claimed is:
 1. An idler device for a magneticrecording/reproducing apparatus comprising: a clutch shaft verticallycoupled to a main chassis; an idler arm installed rotatable centeringaround the clutch shaft by having an mounting portion elasticallyengaged to the clutch shaft in a snap method in the direction of theside of the clutch shaft at one portion; an idler shaft provided at theother portion of the idler arm; an idler gear rotatably installed at theidler arm centering around the idler shaft, for selectively transmittinga driving force according to a rotational direction; and a pressingelastic member supported by an end portion of the idler shaft, forelastically pressing the idler gear in the direction of the idler arm.2. The device of claim 1, wherein the clutch shaft is provided with asupporting portion at its side, and the mounting portion of the idlerarm is supported by being coupled between the main chassis and thesupporting portion of the clutch shaft.
 3. The device of claim 1,wherein a protrusion portion is formed at the end portion of the idlershaft to support the pressing elastic member, and the pressing elasticmember is supported by the protrusion portion and made of a disk-shapedplate spring providing an elastic force to the idler gear.
 4. An idlerdevice for a magnetic recording/reproducing apparatus comprising: arotational central shaft vertically coupled to a main chassis; and anidler arm having an mounting portion elastically engaged to therotational central shaft in a snap method at the side of the rotationalcentral shaft and an idler gear installed at the opposite of themounting portion, for selectively transmitting a driving force accordingto a rotational direction.
 5. The device of claim 4, wherein therotational central shaft is a clutch shaft.
 6. The device of claim 4,wherein the rotational central shaft is press-fit to a fixing hole ofthe main chassis and fixed in a riveting method.
 7. The device of claim4, wherein the rotational central shaft includes a supporting portionformed at its circumferential face, and the mounting portion of theidler arm is supported by being coupled between the main chassis and thesupporting portion of the rotational central shaft.
 8. The device ofclaim 7, wherein the supporting portion of the rotational central shaftis annularly protruded from the circumference of the rotational centralshaft.
 9. The device of claim 4, wherein the mounting portion of theidler arm includes a shaft insertion portion with one side opened sothat the rotational central shaft can be inserted thereinto and aseparation preventing unit formed at the opening portion of the shaftinsertion portion, for not allowing separation from the rotationalcentral shaft.
 10. The device of claim 9, wherein the separationpreventing unit is elastic legs elastically protruded in the directionof the shaft insertion portion from the opened portion of the mountingportion.
 11. The device of claim 10, wherein a front end portion theelastic legs contacts the circumferential face of the rotational centralshaft and the space between each elastic leg is smaller than thediameter of the rotational central shaft.
 12. The device of claim 10,wherein the shaft insertion portion is provided with a semicircularhitching portion closely attached to the rotational central shaft at theportion facing the elastic leg.
 13. An idler device of a magneticrecording/reproducing apparatus comprising: an idler arm installedrotatable centering around a rotational shaft of which one side is fixedat a main chassis; an idler shaft provided at the other side of theidler arm; an idler gear rotatably installed at the idler arm centeringaround the idler shaft, for selectively transferring a driving force inthe rotational direction; and a pressing elastic member supported by theend portion of the idler shaft and elastically pressing the idler gearin the direction of the idler arm.
 14. The device of claim 13, whereinthe idler arm and the idler shaft are integrally formed.
 15. The deviceof claim 13, wherein a protrusion portion is formed at the end portionof the idler shaft, at which the pressing elastic member is installedand supported.
 16. The device of claim 13, wherein the pressing elasticmember is formed as a disk-type plate spring.
 17. The device of claim13, wherein the pressing elastic member comprises: a central plateinserted into and supported by the idler shaft; a pressing ring closelyattached to the idler gear; and elastic legs connecting the centralplate and the pressing ring and having an elastic force.
 18. The deviceof claim 17, wherein the central plate has stoppers protruded so as forthe central plate to be coupled and supported at the both sides of theidler shaft.
 19. The device of claim 17, wherein the elastic legs areextended to have a scroll structure at the circumference of the centralplate.
 20. The device of claim 17, wherein the elastic legs areslantingly connected so as for the central plate and the pressing ringto have a predetermined height difference.